1. Field of the Invention
The present invention relates to a magnetic transducer in a magnetic data storage system, and more particularly to a magnetic transducer having a wear indication feature which improves the reliability, availability and serviceability of the magnetic storage system.
2. Description of the Related Art
Magnetic disk drives are information storage devices which utilize at least one rotatable disk with concentric data tracks containing the information, one or more transducers (or "heads") for reading data from and/or writing data to the various tracks, and a head positioning actuator connected to the transducer for moving it to the desired track and maintaining it over the track centerline during read or write operations. Referring to FIG. 1, which shows a prior art head suspension assembly, the transducer 20 is attached to a slider 26 which is biased against the data surface of the disk 24. In alternative prior art assemblies, the slider may fly slightly above the surface of the disk supported by an air bearing generated by the rotation of the disk. The slider 26 is mounted on a support arm of the positioning actuator (not shown) by way of a suspension 25. The suspension 25 provides dimensional stability between the slider 26 and actuator, and controlled flexibility in slight vertical as well as pitch and roll motions (gimbaled motions) of the slider during its relative motion above the rotating magnetic disk surface.
With a push for higher data densities (the amount of data which can be recorded on a disk), it becomes a challenge to format the disk surface with narrower data tracks and narrower inter-track spacings in order to pack more data tracks on the disk surface. A significant limitation on data density is the spacing between the transducer and the disk surface. Generally, the smaller the spacing between a transducer and a disk, the higher the data density possible, as the magnetic flux in relation to the transducer is more focused at a smaller area on the disk surface so as to improve data resolution. As previously mentioned, one type of transducer in a magnetic disk storage system is designed to be mounted on a slider which rides on a cushion of air or an air bearing generated by the rotating disk in close proximity to the disk surface. For another type of transducer, it is designed to be mounted on a slider with the transducer in contact with the rotating disk surface. The transducer of the latter type is often referred to as contact transducer. With everything else being equal, it is possible to achieve a higher data density using a contact transducer than an air bearing type transducer.
The contact transducer is not without limitation. Referring to FIG. 1, the contact transducer 20 has a tip structure 22 (schematically shown) which is configured to detect a change in magnetic flux when reading data from the magnetic disk 24 and/or cause a change in magnetic flux when writing data onto the magnetic disk 24 as the transducer 20 is moved across the magnetic disk 24. This tip 22 has an operational thickness T in the order of a few microns thick. By nature of a contact transducer, the tip 22 is inevitably subject to wear from abrasion by the magnetic disk 24 once the disk drive has been placed into operation. The slider 26 which is made of a harder material than the tip 22 slows down the wear process to some extent. However, eventually, prolong wear of the transducer tip 22 would lead to inadequate or unreliable transducing functions and ultimate failure of the transducer 20, which would in turn lead to read and/or write failure of the disk drive system thereby putting it out of service. When the transducer fails, data integrity may be affected.
It is therefore desirable for an user of a disk drive system to be able to anticipate the wear induced failure point of the contact transducer `on-the-fly` during actual operation of the disk drive system, so that data can be safely archived prior to actual transducer failure, and so that the failing transducer or the entire disk drive system may be timely replaced at a convenient time with the least disruption to normal disk drive operations. Further, in accomplishing the foregoing, it is desirable to keep any additional structure to the transducer, slider or the suspension assembly therefor to a minimum. This is to minimize adding weight and inertia to the slider/suspension assembly which would otherwise negatively affect the mechanical performance of the disk drive system and increase complexity of manufacturing.